It is well known to utilize dark colored chips of wood as a mulch material in gardening applications. In such applications, the coloration of the wood chip material is critical to the marketability of the product. Particularly, wood chips prepared from the bark of certain tress, especially aromatic trees such as pine and cedar trees, have high marketability. The distinctive color of such mulches, particularly the bark mulches, is typically a dark shade ranging from a reddish-orange color to a deep brown color. At least as important as the exact color is a uniformity of color in the mulch. A blonde colored mulch seems to lack the attraction of a dark mulch material for gardening applications.
Although the preferable material in a mulch may be the bark, it is clear that the supply of such mulch is limited and generally not expandable without expanding the amount of wood being felled. At the same time, however, there is a significant amount of lumber, particularly light colored lumber as used in producing pallets, that is disposed of yearly. If this material were capable of being converted into an aesthetically pleasing mulch material that would compete favorably with the bark mulches on the market, the inherent problems of land filling with this material could be avoided. Additionally, the supply of available light colored lumber of this sort is at least adequate to meet the demand that would be made for the preferred mulch material. In this way, an additional supply of a desired product is brought to the market without increasing the destruction of forest lands and an ecologically sound disposition of the material, otherwise landfilled, is also achieved.
It is also known that surface oxidation of light colored lumber will occur naturally, resulting in a darker colored material. It is not generally feasible to use this natural darkening through oxidation, however, to prepare a dark colored mulch material. This is because the natural oxidation is subject to variation among the wood, so that achievement of a uniform color is certainly not at all probable. Additionally, it is desirable to move the wood through a processing facility in a rapid fashion so that no piles of ground wood are sitting around waiting for the natural oxidation of the surfaces to occur. It is well known that, under proper weather conditions, a ground wood pile can spontaneously combust due to the heat generated internally to the pile by the oxidation process.